iMechanica - Review - Comments

I did find the paper in the end --- it is published in JoMMS!

Mike Ciavarella — Thu, 28 Aug 2008 04:41:35 -0400

http://pjm.math.berkeley.edu/jomms/2008/3-5/p03.xhtml

Renormalizations in solid and fracture mechanics

H. D. Bui

Vol. 3 (2008), No. 5, 853-866

Abstract

We show how some inconsistencies and infinities arising in solid and fracture
mechanics can be avoided by renormalization techniques widely used in theoretical
physics. Some examples, already known in solid mechanics or recently discovered in fracture mechanics, are given as illustrations.

Keywords

fracture mechanics, divergence, renormalization, regularization

Authors

           H. D. Bui

           Laboratoire de Mécanique des Solides (CNRS UMR 7649)
École Polytechnique
Palaiseau Cedex 91128
France

LaMSID/CNRS UMR 2932
EDF Clamart
France

HI all, The reviewer

hamanh — Fri, 18 Apr 2008 07:47:35 -0400

HI all,

The reviewer found the paper interesting because he reads the paper !. Until one does not have the paper, one cannot know how interesting it is !!

Hamanh

interesting?

Arash_Yavari — Wed, 16 Apr 2008 01:00:00 -0400

Dear Michele:

With all the due respect, I don't see why this review paper should be
interesting. The author calls something "strongly emotionally-based
disputes" without giving any reason for his/her claim. Other than that,
I see some trivial history and nothing more. Maybe I'm missing
something here?

Regards,
Arash

Hi Michele,

hamanh — Mon, 14 Apr 2008 05:13:35 -0400

Hi Michele,

Very interestingly. He is one of excellent mechanians works at Ecole Polytechnique. He is also the one pioneers th dual J intergral in Fracture Mechanics.

Hamanh

Surface stress effect on shear modulus

hamed hamed — Fri, 04 Apr 2008 13:04:00 -0400

does surface stress enfluence on shear modulus?

Lu's paper - some explanation

Stanislaw Kalicinski — Thu, 22 Mar 2007 09:17:43 -0400

Hi,

Can anybody help me with understanding of some terms from Lu's paper? It seems I lack of some principle knowledge about physics at surfaces. My background is mostly micro-electronics and MEMS but I'm doing PhD in reliability of MEMS and would like to understand more what is happening on the surface of semiconductors (from mechanical point of view) in case of adsorption-desorption of different spieces.

I do not understand what is strain-dependent and independent surface stress, the two terms mentioned in the paper mentioned by Mr. Pradeep.

What is still not clear to me is whether the surface stress affect the resonance frequency of cantilevers or not. It seems that what Lagowski have written is not true (see Gurtin et al) but Lu says it true in one case but not in another (strain-dependent surface stress). This is very confusing.

Could you indicate what I should read (books, papers) first to understand it?

Thank you in advance!

ask for a help

Zaiwang Huang — Mon, 18 Dec 2006 21:36:11 -0500

Dear weixu your result is really interesting for me. for my current research, I encounter a problem similar to you. in my experiment of uniaxial compression for micropillar, the elastic modulus of different diameter(micro to submicro-scale) column vary largely, could you provide me some your research details? thanks a lot

Thank you I have posted it!

Weixu Zhang — Mon, 18 Dec 2006 21:17:54 -0500

Thank you Prof. Sharma I have posted the paper on the effect of surface energy on yield strength!

You can (nearly) always post a pre-print.

Pradeep Sharma — Mon, 18 Dec 2006 19:51:24 -0500

You can always post a pre-print. Far as I know, this is not a violation of copyright. You can check rules for each journal on this web site.

To add an attachment, you have to create your own new post which I would encourage you to do.

I am glad to post my manuscript here, but I don't know copyrigh

Weixu Zhang — Mon, 18 Dec 2006 19:32:18 -0500

Prof. Sharma.
Yes I am glad to post my manuscript here, and I think it may be helpful to understand the surface effect more.

But I know nothing about the copyright problem. It is just a manuscript submited to APL under review. Can I post it here ? Of course it is my own manuscript. Another question is that if I have the rights to allow others to download my papers published in a journal?
It is part of my doctoral dissertation. If I can post it here, who will please tell me how to add an attachment here?

Please do post it...

Pradeep Sharma — Mon, 18 Dec 2006 11:10:38 -0500

Weixu, please do post your paper here. Along with me, I am sure, others will be interested to look at it.

Hi Prof. Sharma would like to see my manuscript on surface effe

Weixu Zhang — Mon, 18 Dec 2006 10:28:45 -0500

Hi Prof. Sharma would like to see my manuscript on surface effect on the yield strength of material with nano-inhomogeneities?

I investigated the surface effect on plastic deformation of nanomaterials. The surface effect has influence not only on the elastic moduli but also plastic deformation of materials with nano-inhomogeneities.

Thank you for this very nice

Philip LeDuc — Mon, 25 Sep 2006 19:22:52 -0400

Thank you for this very nice information. This type of technology is becoming more essential as detection of molecules has a wide variety of fields. From my personal interest, quantification of molecules will be a huge advantage when trying to dissect the complex interactions happening at the cellular level. As there are hundreds of thousands of different types of molecules as well as billions of molecules in a single cell, the ability to quantify them may be a tremendous advantage. I applaud you again on this work and look forward to reading more on it in the future! Best wishes! Philip LeDuc

response to Wei Hong's comment

Pradeep Sharma — Sun, 24 Sep 2006 19:28:05 -0400

Wei,

I agree with all of your points. Gurtin's expression is the correct one. The residual surface tension should play no role in this.

Kilho, it would be interesting to take another look at your findings with the aid of Gurtin's expression (and interpreting the resonant frequency change due to surface elasticity rather than surface tension). Incidentally, the following (more recent) paper might be germane as well: Surface stress effects on the resonance properties of cantilever sensors, Lu et al, PRB, 72 (8), 2005, 085405

It more or less summarizes most of the things we have discussed in this post.

The governing equation might be wrong

Wei Hong — Sun, 24 Sep 2006 17:46:12 -0400

Dear Kilho,

I am afraid the governing equation you used might be wrong.

Eq. (1), or eq (21) in Ren and Zhao's paper, is the vibration equation of a beam under external distributed axial load (tau).

It might be a misunderstanding of "surface stress". Surface stress is the variation of surface energy with respect to the strain, often writen as a constant (surface tension) plus a term linear in strain. Neither term depends on spacial coordinates. And the result of it is just a constant tension / compression in the substrate/surface layer. Even in a beam bent by the surface stress, there's no shear stress between the bulk and the surface layer, except on the very end.

Secondly, surface stress is a internal force rather than external. If the central part of the beam is under compression, the surface must be under tension, and they are balanced. One cannot analys the central part of the beam as a prestressed beam, while neglecting the surface tension. This is a similar mistake as that made by Lagowski et al, pointed out by Gurtin et al.

Gurtin et al use energy method to analys the problem, and the result is quite intuitive: a constant surface tension will never change the resonant frequency, only the stiffness of the surface (which makes a thin beam seemingly stiffer) shifts the vibration frequency, just as Pradeep mentioned.

Correct me if I am wrong.